A couple of weeks ago on a flight I sat next to a person who's deeply involved in the ATI negotiations - can't say for who, but trust me, deep into it. NOT a regulator BTW.
Their internal assessment is that ATI will probably be granted (they were guessing in the first or second quarters of CY 2010) provided AA and (mainly) BA agree to give up some LHR slots. It's all about the LHR slots, according to this person.